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Madsen, Alexander K
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Publications (10 of 365) Show all publications
Aaboud, M., Bergeås, E. K., Bokan, P., Brenner, R., Ekelöf, T., Ellert, M., . . . Zwalinski, L. (2018). Measurement of the W-boson mass in pp collisions at root s=7 TeV with the ATLAS detector. European Physical Journal C, 78(11), Article ID 110.
Open this publication in new window or tab >>Measurement of the W-boson mass in pp collisions at root s=7 TeV with the ATLAS detector
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2018 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 78, no 11, article id 110Article in journal (Refereed) Published
Abstract [en]

A measurement of the mass of the W boson is presented based on proton-proton collision data recorded in 2011 at a centre-of-mass energy of 7 TeV with the ATLAS detector at the LHC, and corresponding to 4.6 fb(-1) of integrated luminosity. The selected data sample consists of 7.8 x 10(6) candidates in the W -> mu nu channel and 5.9 x 10(6) candidates in the W -> e nu channel. The W-boson mass is obtained from template fits to the reconstructed distributions of the charged lepton transverse momentum and of the W boson transverse mass in the electron and muon decay channels, yielding

m(W) = 80370 +/- 7 (stat.) +/- 11(exp. syst.)

+/- 14 (mod. syst.) MeV

= 80370 +/- 19 MeV,

where the first uncertainty is statistical, the second corresponds to the experimental systematic uncertainty, and the third to the physics-modelling systematic uncertainty. A measurement of the mass difference between the W+ and W- bosons yields m(W+) - m(W-) = -29 +/- 28 MeV.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-347255 (URN)10.1140/epjc/s10052-017-5475-4 (DOI)000424385500005 ()
Note

Correction in: EUROPEAN PHYSICAL JOURNAL C, Volume: 78, Issue: 11, Article Number: 898, DOI: 10.1140/epjc/s10052-018-6354-3

ATLAS Collaboration, for complete list of authors see http://dx.doi.org/10.1140/epjc/s10052-017-5475-4

Available from: 2018-03-28 Created: 2018-03-28 Last updated: 2019-01-17Bibliographically approved
Aaboud, M., Bergeås, E. K., Brenner, R., Ekelöf, T., Ellert, M., Ferrari, A., . . . Zwalinski, L. (2017). A measurement of the calorimeter response to single hadrons and determination of the jet energy scale uncertainty using LHC Run-1 pp-collision data with the ATLAS detector. European Physical Journal C, 77(1), Article ID 26.
Open this publication in new window or tab >>A measurement of the calorimeter response to single hadrons and determination of the jet energy scale uncertainty using LHC Run-1 pp-collision data with the ATLAS detector
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2017 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 77, no 1, article id 26Article in journal (Refereed) Published
Abstract [en]

A measurement of the calorimeter response to isolated charged hadrons in the ATLAS detector at the LHC is presented. This measurement is performed with 3.2 nb(-1) of proton-proton collision data at root s = 7 TeV from 2010 and 0.1 nb(-1) of data at root s = 8 TeV from 2012. A number of aspects of the calorimeter response to isolated hadrons are explored. After accounting for energy deposited by neutral particles, there is a 5% discrepancy in the modelling, using various sets of GEANT4 hadronic physics models, of the calorimeter response to isolated charged hadrons in the central calorimeter region. The description of the response to anti-protons at low momenta is found to be improved with respect to previous analyses. The electromagnetic and hadronic calorimeters are also examined separately, and the detector simulation is found to describe the response in the hadronic calorimeter well. The jet energy scale uncertainty and correlations in scale between jets of different momenta and pseudorapidity are derived based on these studies. The uncertainty is 2-5% for jets with transverse momenta above 2 TeV, where this method provides the jet energy scale uncertainty for ATLAS.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-319386 (URN)10.1140/epjc/s10052-016-4580-0 (DOI)000392335600003 ()28260979 (PubMedID)
Note

ATLAS Collaboration, for complete list of authors see https://doi.org/10.1140/epjc/s10052-016-4580-0

Funding: We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently. We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW and FWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; CONICYT, Chile; CAS, MOST and NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR and VSC CR, Czech Republic; DNRF and DNSRC, Denmark; IN2P3-CNRS, CEA-DSM/IRFU, France; GNSF, Georgia; BMBF, HGF, and MPG, Germany; GSRT, Greece; RGC, Hong Kong SAR, China; ISF, I-CORE and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; FOM and NWO, Netherlands; RCN, Norway; MNiSW and NCN, Poland; FCT, Portugal; MNE/IFA, Romania; MES of Russia and NRC KI, Russian Federation; JINR; MESTD, Serbia; MSSR, Slovakia; ARRS and MIZS, Slovenia; DST/NRF, South Africa; MINECO, Spain; SRC and Wallenberg Foundation, Sweden; SERI, SNSF and Cantons of Bern and Geneva, Switzerland; MOST, Taiwan; TAEK, Turkey; STFC, United Kingdom; DOE and NSF, United States of America. In addition, individual groups and members have received support from BCKDF, the Canada Council, CANARIE, CRC, Compute Canada, FQRNT, and the Ontario Innovation Trust, Canada; EPLANET, ERC, FP7, Horizon 2020 and Marie Sklodowska-Curie Actions, European Union; Investissements d'Avenir Labex and Idex, ANR, Region Auvergne and Fondation Partager le Savoir, France; DFG and AvH Foundation, Germany; Herakleitos, Thales and Aristeia programmes co-financed by EU-ESF and the Greek NSRF; BSF, GIF and Minerva, Israel; BRF, Norway; Generalitat de Catalunya, Generalitat Valenciana, Spain; the Royal Society and Leverhulme Trust, United Kingdom. The crucial computing support from all WLCG partners is acknowledged gratefully, in particular from CERN, the ATLAS Tier-1 facilities at TRIUMF (Canada), NDGF (Denmark, Norway, Sweden), CC-IN2P3 (France), KIT/GridKA (Germany), INFN-CNAF (Italy), NL-T1 (Netherlands), PIC (Spain), ASGC (Taiwan), RAL (UK) and BNL (USA), the Tier-2 facilities worldwide and large non-WLCG resource providers. Major contributors of computing resources are listed in Ref. [41].

Available from: 2017-04-04 Created: 2017-04-04 Last updated: 2017-11-29Bibliographically approved
Aaboud, M., Bergeås Kuutmann, E., Bokan, P., Brenner, R., Ekelöf, T., Ellert, M., . . . Zwalinski, L. (2017). Determination of the strong coupling constant alpha(s) from transverse energy-energy correlations in multijet events at root s=8 TeV using the ATLAS detector. European Physical Journal C, 77(12), Article ID 872.
Open this publication in new window or tab >>Determination of the strong coupling constant alpha(s) from transverse energy-energy correlations in multijet events at root s=8 TeV using the ATLAS detector
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2017 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 77, no 12, article id 872Article in journal (Refereed) Published
Abstract [en]

Measurements of transverse energy-energy correlations and their associated asymmetries in multi-jet events using the ATLAS detector at the LHC are presented. The data used correspond to vs = 8 TeV proton-proton collisions with an integrated luminosity of 20.2 fb(-1). The results are presented in bins of the scalar sum of the transverse momenta of the two leading jets, unfolded to the particle level and compared to the predictions from Monte Carlo simulations. A comparison with next-to-leading-order perturbative QCD is also performed, showing excellent agreement within the uncertainties. From this comparison, the value of the strong coupling constant is extracted for different energy regimes, thus testing the running of alpha(s)(mu) predicted in QCD up to scales over 1 TeV. A global fit to the transverse energy-energy correlation distributions yields alpha(s)(m(Z)) = 0.1162 +/- 0.0011 (exp.)(-0.0070)(+0.0084) (theo.), while a global fit to the asymmetry distributions yields a value of alpha(s)(m(Z)) = 0.1196 +/- 0.0013 (exp.)(-0.0045)(+0.0075) (theo.).

Place, publisher, year, edition, pages
Springer, 2017
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-342063 (URN)10.1140/epjc/s10052-017-5442-0 (DOI)000418364300002 ()
Note

ATLAS Collaboration, for complete list of authors see http://dx.doi.org/10.1140/epjc/s10052-017-5442-0

We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently. We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW and FWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; CONICYT, Chile; CAS, MOST and NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR and VSC CR, Czech Republic; DNRF and DNSRC, Denmark; IN2P3-CNRS, CEA-DRF/IRFU, France; SRNSF, Georgia; BMBF, HGF, and MPG, Germany; GSRT, Greece; RGC, Hong Kong SAR, China; ISF, I-CORE and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; NWO, Netherlands; RCN, Norway; MNiSW and NCN, Poland; FCT, Portugal; MNE/IFA, Romania; MES of Russia and NRC KI, Russian Federation; JINR; MESTD, Serbia; MSSR, Slovakia; ARRS and MIZŠ, Slovenia; DST/NRF, South Africa; MINECO, Spain; SRC and Wallenberg Foundation, Sweden; SERI, SNSF and Cantons of Bern and Geneva, Switzerland; MOST, Taiwan; TAEK, Turkey; STFC, United Kingdom; DOE and NSF, United States of America. In addition, individual groups and members have received support from BCKDF, the Canada Council, CANARIE, CRC, Compute Canada, FQRNT, and the Ontario Innovation Trust, Canada; EPLANET, ERC, ERDF, FP7, Horizon 2020 and Marie Skłodowska-Curie Actions, European Union; Investissements d’Avenir Labex and Idex, ANR, Région Auvergne and Fondation Partager le Savoir, France; DFG and AvH Foundation, Germany; Herakleitos, Thales and Aristeia programmes co-financed by EU-ESF and the Greek NSRF; BSF, GIF and Minerva, Israel; BRF, Norway; CERCA Programme Generalitat de Catalunya, Generalitat Valenciana, Spain; the Royal Society and Leverhulme Trust, United Kingdom. The crucial computing support from all WLCG partners is acknowledged gratefully, in particular from CERN, the ATLAS Tier-1 facilities at TRIUMF (Canada), NDGF (Denmark, Norway, Sweden), CC-IN2P3 (France), KIT/GridKA (Germany), INFN-CNAF (Italy), NL-T1 (Netherlands), PIC (Spain), ASGC (Taiwan), RAL (UK) and BNL (USA), the Tier-2 facilities worldwide and large non-WLCG resource providers. Major contributors of computing resources are listed in Ref. [87].

Available from: 2018-02-19 Created: 2018-02-19 Last updated: 2018-02-19Bibliographically approved
Aaboud, M., Bergeås, E. K., Bokan, P., Brenner, R., Ekelöf, T., Ellert, M., . . . Zwalinski, L. (2017). Evidence for light-by-light scattering in heavy-ion collisions with the ATLAS detector at the LHC. Nature Physics, 13(9), 852-858
Open this publication in new window or tab >>Evidence for light-by-light scattering in heavy-ion collisions with the ATLAS detector at the LHC
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2017 (English)In: Nature Physics, ISSN 1745-2473, E-ISSN 1745-2481, Vol. 13, no 9, p. 852-858Article in journal (Refereed) Published
Abstract [en]

Light-by-light scattering (gamma gamma -> gamma gamma) is a quantum-mechanical process that is forbidden in the classical theory of electrodynamics. This reaction is accessible at the Large Hadron Collider thanks to the large electromagnetic field strengths generated by ultra-relativistic colliding lead ions. Using 480 mu b(-1) of lead-lead collision data recorded at a centre-of-mass energy per nucleon pair of 5.02 TeV by the ATLAS detector, here we report evidence for light-by-light scattering. A total of 13 candidate events were observed with an expected background of 2.6 +/- 0.7 events. After background subtraction and analysis corrections, the fiducial cross-section of the process Pb + Pb (gamma gamma) -> Pb-(center dot) + Pb-(center dot) gamma gamma, for photon transverse energy E-T > 3 GeV, photon absolute pseudorapidity vertical bar eta vertical bar < 2.4, diphoton invariant mass greater than 6 GeV, diphoton transverse momentum lower than 2 GeV and diphoton acoplanarity below 0.01, is measured to be 70 +/- 24 (stat.) +/- 17 (syst.) nb, which is in agreement with the standard model predictions.

Place, publisher, year, edition, pages
Nature Publishing Group, 2017
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-336462 (URN)10.1038/nphys4208 (DOI)000409235100017 ()
Note

ATLAS Collaboration, for complete list of authors see https://doi.org/10.1038/nphys4208

Funding:  We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently. We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW and FWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; CONICYT, Chile; CAS, MOST and NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR and VSC CR, Czech Republic; DNRF and DNSRC, Denmark; IN2P3-CNRS, CEA-DSM/IRFU, France; GNSF, Georgia; BMBF, HGF and MPG, Germany; GSRT, Greece; RGC, Hong Kong SAR, China; ISF, I-CORE and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; FOM and NWO, Netherlands; RCN, Norway; MNiSW and NCN, Poland; FCT, Portugal; MNE/IFA, Romania; MES of Russia and NRC KI, Russian Federation; JINR; MESTD, Serbia; MSSR, Slovakia; ARRS and MIZŠ, Slovenia; DST/NRF, South Africa; MINECO, Spain; SRC and Wallenberg Foundation, Sweden; SERI, SNSF and Cantons of Bern and Geneva, Switzerland; MOST, Taiwan; TAEK, Turkey; STFC, United Kingdom; DOE and NSF, United States of America. In addition, individual groups and members have received support from BCKDF, the Canada Council, CANARIE, CRC, Compute Canada, FQRNT, and the Ontario Innovation Trust, Canada; EPLANET, ERC, ERDF, FP7, Horizon 2020 and Marie Skłodowska-Curie Actions, European Union; Investissements d’Avenir Labex and Idex, ANR, Région Auvergne and Fondation Partager le Savoir, France; DFG and AvH Foundation, Germany; Herakleitos, Thales and Aristeia programmes co-financed by EU-ESF and the Greek NSRF; BSF, GIF and Minerva, Israel; BRF, Norway; CERCA Programme Generalitat de Catalunya, Generalitat Valenciana, Spain; the Royal Society and Leverhulme Trust, United Kingdom. The crucial computing support from all WLCG partners is acknowledged gratefully, in particular from CERN, the ATLAS Tier-1 facilities at TRIUMF (Canada), NDGF (Denmark, Norway, Sweden), CC-IN2P3 (France), KIT/GridKA (Germany), INFN-CNAF (Italy), NL-T1 (Netherlands), PIC (Spain), ASGC (Taiwan), RAL (UK) and BNL (USA), the Tier-2 facilities worldwide and large non-WLCG resource providers. Major contributors of computing resources are listed in ref. 51.

Available from: 2017-12-14 Created: 2017-12-14 Last updated: 2017-12-14Bibliographically approved
Aaboud, M., Bergeås Kuutmann, E., Bokan, P., Brenner, R., Ekelöf, T., Ellert, M., . . . Zwalinski, L. (2017). Femtoscopy with identified charged pions in proton-lead collisions at root s(NN)=5.02 TeV with ATLAS. Physical Review C: Covering Nuclear Physics, 96(6), Article ID 064908.
Open this publication in new window or tab >>Femtoscopy with identified charged pions in proton-lead collisions at root s(NN)=5.02 TeV with ATLAS
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2017 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 96, no 6, article id 064908Article in journal (Refereed) Published
Abstract [en]

Bose-Einstein correlations between identified charged pions are measured for p+Pb collisions at root s(NN) = 5.02 TeV using data recorded by the ATLAS detector at the CERN Large Hadron Collider corresponding to a total integrated luminosity of 28 nb(-1). Pions are identified using ionization energy loss measured in the pixel detector. Two-particle correlation functions and the extracted source radii are presented as a function of collision centrality as well as the average transverse momentum (k(T)) and rapidity (y*(pi pi)) of the pair. Pairs are selected with a rapidity -2 < y*(pi pi) < 1 and with an average transverse momentum 0.1 < k(T) < 0.8 GeV. The effect of jet fragmentation on the two-particle correlation function is studied, and a method using opposite-charge pair data to constrain its contributions to the measured correlations is described. The measured source sizes are substantially larger in more central collisions and are observed to decrease with increasing pair k(T). A correlation of the radii with the local charged-particle density is demonstrated. The scaling of the extracted radii with the mean number of participating nucleons is also used to compare a selection of initial-geometry models. The cross term R-ol is measured as a function of rapidity, and a nonzero value is observed with 5.1 sigma combined significance for -1 < y*pi pi < 1 in the most central events.

Place, publisher, year, edition, pages
American Physical Society, 2017
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-342080 (URN)10.1103/PhysRevC.96.064908 (DOI)000418917300004 ()
Note

ATLAS Collaboration, for complete list of authors see http://dx.doi.org/10.1103/PhysRevC.96.064908

We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently. We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW and FWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; CONICYT, Chile; CAS, MOST, and NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR, and VSC CR, Czech Republic; DNRF and DNSRC, Denmark; IN2P3-CNRS, CEA-DSM/IRFU, France; SRNSF, Georgia; BMBF, HGF, and MPG, Germany; GSRT, Greece; RGC, Hong Kong SAR, China; ISF, I-CORE, and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; NWO, Netherlands; RCN, Norway; MNiSW and NCN, Poland; FCT, Portugal; MNE/IFA, Romania; MES of Russia and NRC KI, Russian Federation; JINR; MESTD, Serbia; MSSR, Slovakia; ARRS and MIZŠ, Slovenia; DST/NRF, South Africa; MINECO, Spain; SRC and Wallenberg Foundation, Sweden; SERI, SNSF, and Cantons of Bern and Geneva, Switzerland; MOST, Taiwan; TAEK, Turkey; STFC, United Kingdom; DOE and NSF, United States of America. In addition, individual groups and members have received support from BCKDF, the Canada Council, CANARIE, CRC, Compute Canada, FQRNT, and the Ontario Innovation Trust, Canada; EPLANET, ERC, ERDF, FP7, Horizon 2020, and Marie Skłodowska-Curie Actions, European Union; Investissements d'Avenir Labex and Idex, ANR, Région Auvergne, and Fondation Partager le Savoir, France; DFG and AvH Foundation, Germany; Herakleitos, Thales, and Aristeia programs cofinanced by EU-ESF and the Greek NSRF; BSF, GIF, and Minerva, Israel; BRF, Norway; CERCA Programme Generalitat de Catalunya, Generalitat Valenciana, Spain; the Royal Society and Leverhulme Trust, United Kingdom. The crucial computing support from all WLCG partners is acknowledged gratefully, in particular from CERN, the ATLAS Tier-1 facilities at TRIUMF (Canada), NDGF (Denmark, Norway, Sweden), CC-IN2P3 (France), KIT/GridKA (Germany), INFN-CNAF (Italy), NL-T1 (Netherlands), PIC (Spain), ASGC (Taiwan), RAL (UK), and BNL (USA), the Tier-2 facilities worldwide, and large non-WLCG resource providers. Major contributors of computing resources are listed in Ref. [76].

Available from: 2018-02-19 Created: 2018-02-19 Last updated: 2018-09-05Bibliographically approved
Aaboud, M., Bergeås Kuutmann, E., Brenner, R., Ekelöf, T., Ellert, M., Ferrari, A., . . . Zwalinski, L. (2017). High-ET isolated-photon plus jets production in pp collisions at √s=8 TeV with the ATLAS detector. Nuclear Physics B, 918, 257-316
Open this publication in new window or tab >>High-ET isolated-photon plus jets production in pp collisions at √s=8 TeV with the ATLAS detector
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2017 (English)In: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 918, p. 257-316Article in journal (Refereed) Published
Abstract [en]

The dynamics of isolated-photon plus one-, two- and three-jet production in pp collisions at a centre-of-mass energy of 8 TeV are studied with the ATLAS detector at the LHC using a data set with an integrated luminosity of 20.2 fb-1. Measurements of isolated-photon plus jets cross sections are presented as functions of the photon and jet transverse momenta. The cross sections as functions of the azimuthal angle between the photon and the jets, the azimuthal angle between the jets, the photon-jet invariant mass and the scattering angle in the photon-jet centre-of-mass system are presented. The pattern of QCD radiation around the photon and the leading jet is investigated by measuring jet production in an annular region centred on each object; enhancements are observed around the leading jet with respect to the photon in the directions towards the beams. The experimental measurements are compared to several different theoretical calculations, and overall a good description of the data is found.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-326386 (URN)10.1016/j.nuclphysb.2017.03.006 (DOI)000401097200012 ()
Funder
Australian Research CouncilDanish National Research FoundationSwedish Research CouncilEU, European Research CouncilEU, FP7, Seventh Framework ProgrammeEU, Horizon 2020German Research Foundation (DFG)
Note

ATLAS Collaboration, for complete list of authors https://doi.org/10.1016/j.nuclphysb.2017.03.006

Funding: We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW and FWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; CONICYT, Chile; CAS, MOST and NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR and VSC CR, Czech Republic; DNRF and DNSRC, Denmark; IN2P3-CNRS, CEA-DSM/IRFU, France; SRNSF, Georgia; BMBF, HGF, and MPG, Germany; GSRT, Greece; RGC, Hong Kong SAR, China; ISF, I-CORE and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; FOM and NWO, Netherlands; RCN, Norway; MNiSW and NCN, Poland; FCT, Portugal; MNE/IFA, Romania; MES of Russia and NRC KI, Russian Federation; JINR; MESTD, Serbia; MSSR, Slovakia; ARRS and MIZS, Slovenia; DST/NRF, South Africa; MINECO, Spain; SRC and Wallenberg Foundation, Sweden; SERI, SNSF and Cantons of Bern and Geneva, Switzerland; MOST, Taiwan; TAEK, Turkey; STFC, United Kingdom; DOE and NSF, United States of America. In addition, individual groups and members have received support from BCKDF, the Canada Council, Canarie, CRC, Compute Canada, FQRNT, and the Ontario Innovation Trust, Canada; EPLANET, ERC, ERDF, FP7, Horizon 2020 and Marie Sklodowska-Curie Actions, European Union; Investissements d'Avenir Labex and Idex, ANR, Region Auvergne and Fondation Partager le Savoir, France; DFG and AvH Foundation, Germany; Herakleitos, Thales and Aristeia programmes co-financed by EU-ESF and the Greek NSRF; BSF, GIF and Minerva, Israel; BRF, Norway; CERCA Programme Generalitat de Catalunya, Generalitat Valenciana, Spain; the Royal Society and Leverhulme Trust, United Kingdom.

Available from: 2017-07-07 Created: 2017-07-07 Last updated: 2017-07-07Bibliographically approved
Aaboud, M., Bergeaas Kuutmann, E., Bokan, P., Brenner, R., Ekelöf, T., Ellert, M., . . . Zwalinski, L. (2017). Jet reconstruction and performance using particle flow with the ATLAS Detector. European Physical Journal C, 77, Article ID 466.
Open this publication in new window or tab >>Jet reconstruction and performance using particle flow with the ATLAS Detector
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2017 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 77, article id 466Article in journal (Refereed) Published
Abstract [en]

This paper describes the implementation and performance of a particle flow algorithm applied to 20.2 fb(-1) of ATLAS data from 8 TeV proton-proton collisions in Run 1 of the LHC. The algorithm removes calorimeter energy deposits due to charged hadrons from consideration during jet reconstruction, instead using measurements of their momenta from the inner tracker. This improves the accuracy of the charged-hadron measurement, while retaining the calorimeter measurements of neutral-particle energies. The paper places emphasis on how this is achieved, while minimising double-counting of charged-hadron signals between the inner tracker and calorimeter. The performance of particle flow jets, formed from the ensemble of signals from the calorimeter and the inner tracker, is compared to that of jets reconstructed from calorimeter energy deposits alone, demonstrating improvements in resolution and pile-up stability.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-332890 (URN)10.1140/epjc/s10052-017-5031-2 (DOI)000405437300002 ()28943792 (PubMedID)
Note

ATLAS Collaboration, for complete list of authors see http://dx.doi.org/10.1140/epjc/s10052-017-5031-2

Available from: 2017-11-02 Created: 2017-11-02 Last updated: 2018-02-02Bibliographically approved
Aaboud, M., Bergeås, E. K., Bokan, P., Brenner, R., Ekelöf, T., Ellert, M., . . . Zwalinski, L. (2017). Measurement of charged-particle distributions sensitive to the underlying event in root s=13 TeV proton-proton collisions with the ATLAS detector at the LHC. Journal of High Energy Physics (JHEP) (3), Article ID 157.
Open this publication in new window or tab >>Measurement of charged-particle distributions sensitive to the underlying event in root s=13 TeV proton-proton collisions with the ATLAS detector at the LHC
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2017 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 3, article id 157Article in journal (Refereed) Published
Abstract [en]

We present charged-particle distributions sensitive to the underlying event, measured by the ATLAS detector in proton-proton collisions at a centre-of-mass energy of 13 TeV, in low-luminosity Large Hadron Collider fills corresponding to an integrated luminosity of 1.6 nb−1. The distributions were constructed using charged particles with absolute pseudorapidity less than 2.5 and with transverse momentum greater than 500 MeV, in events with at least one such charged particle with transverse momentum above 1 GeV. These distributions characterise the angular distribution of energy and particle flows with respect to the charged particle with highest transverse momentum, as a function of both that momentum and of charged-particle multiplicity. The results have been corrected for detector effects and are compared to the predictions of various Monte Carlo event generators, experimentally establishing the level of underlying-event activity at LHC Run 2 energies and providing inputs for the development of event generator modelling. The current models in use for UE modelling typically describe this data to 5% accuracy, compared with data uncertainties of less than 1%.

Place, publisher, year, edition, pages
Springer, 2017
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-325933 (URN)10.1007/JHEP03(2017)157 (DOI)000400027000001 ()
Note

ATLAS Collaboration, for complete list of authors see http://dx.doi.org/10.1007/JHEP03(2017)157

We thank CERN for the very successful operation of the LHC, as well as the support sta from our institutions without whom ATLAS could not be operated eciently.We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW and FWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq andFAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; CONICYT, Chile; CAS, MOSTand NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR and VSC CR,Czech Republic; DNRF and DNSRC, Denmark; IN2P3-CNRS, CEA-DSM/IRFU, France;GNSF, Georgia; BMBF, HGF, and MPG, Germany; GSRT, Greece; RGC, Hong KongSAR, China; ISF, I-CORE and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS,Japan; CNRST, Morocco; FOM and NWO, Netherlands; RCN, Norway; MNiSW and NCN,Poland; FCT, Portugal; MNE/IFA, Romania; MES of Russia and NRC KI, Russian Federation; JINR; MESTD, Serbia; MSSR, Slovakia; ARRS and MIZS, Slovenia; DST/NRF,South Africa; MINECO, Spain; SRC and Wallenberg Foundation, Sweden; SERI, SNSFand Cantons of Bern and Geneva, Switzerland; MOST, Taiwan; TAEK, Turkey; STFC,United Kingdom; DOE and NSF, United States of America. In addition, individual groupsand members have received support from BCKDF, the Canada Council, CANARIE, CRC,Compute Canada, FQRNT, and the Ontario Innovation Trust, Canada; EPLANET, ERC,ERDF, FP7, Horizon 2020 and Marie Sklodowska-Curie Actions, European Union; Investissements d'Avenir Labex and Idex, ANR, Region Auvergne and Fondation Partagerle Savoir, France; DFG and AvH Foundation, Germany; Herakleitos, Thales and Aristeiaprogrammes co-financed by EU-ESF and the Greek NSRF; BSF, GIF and Minerva, Israel;BRF, Norway; CERCA Programme Generalitat de Catalunya, Generalitat Valenciana,Spain; the Royal Society and Leverhulme Trust, United Kingdom. JHEP03(2017)157The crucial computing support from all WLCG partners is acknowledged gratefully,in particular from CERN, the ATLAS Tier-1 facilities at TRIUMF (Canada), NDGF(Denmark, Norway, Sweden), CC-IN2P3 (France), KIT/GridKA (Germany), INFN-CNAF(Italy), NL-T1 (Netherlands), PIC (Spain), ASGC (Taiwan), RAL (U.K.) and BNL(U.S.A.), the Tier-2 facilities worldwide and large non-WLCG resource providers. Major contributors of computing resources are listed in ref. [44].

Available from: 2017-06-29 Created: 2017-06-29 Last updated: 2017-06-29Bibliographically approved
Aaboud, M., Bergeås, E. K., Brenner, R., Ekelöf, T., Ellert, M., Ferrari, A., . . . Zwalinski, L. (2017). Measurement of forward-backward multiplicity correlations in lead-lead, proton-lead, and proton-proton collisions with the ATLAS detector. Physical review C, 95(6), Article ID 064914.
Open this publication in new window or tab >>Measurement of forward-backward multiplicity correlations in lead-lead, proton-lead, and proton-proton collisions with the ATLAS detector
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2017 (English)In: Physical review C, ISSN 2469-9985, Vol. 95, no 6, article id 064914Article in journal (Refereed) Published
Abstract [en]

Two-particle pseudorapidity correlations are measured in root s(NN) = 2.76 TeV Pb + Pb, root s(NN) = 5.02 TeV p+Pb, and root s = 13 TeV pp collisions at the Large Hadron Collider (LHC), with total integrated luminosities of approximately 7 mu b(-1), 28 nb(-1), and 65 nb(-1), respectively. The correlation function CN(eta(1),eta(2))is measured as a function of event multiplicity using charged particles in the pseudorapidity range |eta| < 2.4. The correlation function contains a significant short-range component, which is estimated and subtracted. After removal of the short-range component, the shape of the correlation function is described approximately by 1 + < a(1)(2)>(1/2) eta(1) eta(2) in all collision systems over the full multiplicity range. The values of < a(1)(2)>(1/2) are consistent for the opposite-charge pairs and same-charge pairs, and for the three collision systems at similar multiplicity. The values of < a(1)(2)>(1/2) and the magnitude of the short-range component both follow a power-law dependence on the event multiplicity. The short-range component in p + Pb collisions, after symmetrizing the proton and lead directions, is found to be smaller at a given eta than in pp collisions with comparable multiplicity.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-331597 (URN)10.1103/PhysRevC.95.064914 (DOI)000404470800003 ()
Note

ATLAS Collaboration, for complete list of authors see http://dx.doi.org/10.1103/PhysRevC.95.064914

Available from: 2017-10-16 Created: 2017-10-16 Last updated: 2017-10-16Bibliographically approved
Aaboud, M., Bergeås, E. K., Bokan, P., Brenner, R., Ekelöf, T., Ellert, M., . . . Zwalinski, L. (2017). Measurement of inclusive and differential cross sections in the H -> ZZ* -> 4l decay channel in pp collisions at root s=13 TeV with the ATLAS detector. Journal of High Energy Physics (JHEP), Article ID 132.
Open this publication in new window or tab >>Measurement of inclusive and differential cross sections in the H -> ZZ* -> 4l decay channel in pp collisions at root s=13 TeV with the ATLAS detector
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2017 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, article id 132Article in journal (Refereed) Published
Abstract [en]

Inclusive and differential fiducial cross sections of Higgs boson production in proton-proton collisions are measured in the H -> Z Z* -> 4l decay channel. The proton-proton collision data were produced at the Large Hadron Collider at a centre-of-mass energy of 13 TeV and recorded by the ATLAS detector in 2015 and 2016, corresponding to an integrated luminosity of 36.1 fb(-1). The inclusive fiducial cross section in the H -> Z Z* -> 4l decay channel is measured to be 3.62 +/- 0.50 (stat) (+0.25)(-0.20) (sys) fb, in agreement with the Standard Model prediction of 2.91 +/- 0.13 fb. The cross section is also extrapolated to the total phase space including all Standard Model Higgs boson decays. Several differential fiducial cross sections are measured for observables sensitive to the Higgs boson production and decay, including kinematic distributions of jets produced in association with the Higgs boson. Good agreement is found between data and Standard Model predictions. The results are used to put constraints on anomalous Higgs boson interactions with Standard Model particles, using the pseudo-observable extension to the kappa-framework.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-341845 (URN)10.1007/JHEP10(2017)132 (DOI)000413664600001 ()
Note

ATLAS Collaboration. For a complete list of authors see: http://dx.doi.org/10.1007/JHEP10(2017)132

Available from: 2018-02-15 Created: 2018-02-15 Last updated: 2018-09-05Bibliographically approved
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